The present invention relates to energy-focusing surfaces, such as radio wave antennas, solar concentrators, and the like, and is particularly directed to a compactly stowable antenna reflector that is formed of a thin continuous laminate material containing radial and perimeter stiffening regions or stiffeners. The thinness of the laminate and that of the stiffeners readily allow the reflector to be collapsed into a compact shape that facilitates stowage in a confined volume on board a spacecraft launch vehicle, such as the space shuttle, while also causing the reflector to deploy into and conform with a prescribed energy-focusing surface geometry.
The field of deployable platforms, such as space-deployed energy-directing structures, including radio frequency (RF) antennas, solar concentrators, and the like, has matured substantially in the past decade. What was once a difficult art to master has developed into a number of practical applications by commercial enterprises. A significant aspect of this development has been the reliable deployment of a variety of spacecraft-supported antenna systems, similar to that employed by the NASA tracking data and relay satellite (TDRS). Indeed, commercial spacecraft production has now exceeded military/civil applications, so that there is currently a demand for structural systems with proven reliability and performance, and the ever present requirement for xe2x80x9creduced cost.xe2x80x9d The mission objective for a typical deployable space antenna is to provide reliable RF energy reflection to an energy collector (feed) located at the focus of a prescribed geometry (e.g. parabolic) energy collecting surface.
The current state of parabolic space antenna design is essentially based upon what may be termed a segmented construction approach which, as diagrammatically illustrated in FIGS. 1-4, is configured much like an umbrella. In this type of antenna, a plurality of arcuate segments 1 are connected to a central hub 3, that supports an antenna feed 5. A mechanically advantaged linear actuator (not shown) is used to drive the segments 1 from their stowed or unfurled condition, shown in the side and end views of FIGS. 1 and 2, into a locked, over-driven, position, so as to deploy an Rf reflector surface 7, as shown in the side and end views of FIGS. 3 and 4.
Principal shortcomings of this type of antenna system include the hardware complexity of the antenna reflector, its attendant deployment mechanism, and the considerable stowage volume associated with that structure. As a consequence, new approaches to deployable antenna structures have been sought. The industry desire for these new approaches is based upon the premise that the stowed packaging density for deployable antennas can be significantly increased, while maintaining a deployed reliability that the space community has enjoyed in the past. If the stowed volume can be reduced (and therefore an increase in packaging density for a given weight), launch services can be applied more efficiently.
In accordance with the present invention, these objectives are successfully achieved by configuring the reflector as a continuous laminate of very thin layers of flexible energy-directing medium or material, having a relatively low coefficient of thermal expansion (CTE), such as thin sheets of graphite epoxy and the like. The flexible laminate is shaped to conform with a prescribed energy-focusing surface geometry (e.g., paraboloid). Because of its thinness, the reflector laminate is has reduced weight and is readily collapsible into a folded shape, that facilitates stowage in a restricted volume. In addition, the laminate structure of the invention includes a plurality of radial and perimeter stiffening regions, that not only function to deploy and maintain the reflector in its intended geometric shape, but are configured to facilitate collapsing the reflector laminate into a compact (serpentine) stowed configuration.